In the drilling of deep wells such as oil wells it is necessary to provide the oil well drilling equipment with some means to prevent the well from blowing out when a high pressure production zone is intersected by the well bore during drilling or when some malfunction occurs either to the well drilling apparatus or within the well itself. The well drilling apparatus is therefore typically provided with one or more blow-out preventers having hydraulically energized rams that are forced into engagement with the drill stem passing therethrough. The blow-out preventers cause gripping or in some cases, crushing or positive deformation of the pipe structure in order to retain the pipe within the well and prevent it from being blown out of the well by high pressure well fluid. Immediately below the lowermost blow-out preventer of the well drilling structure may be provided an injection spool having a conduit connection allowing connection of a flow line to the spool structure, which flow line may be interconnected between the spool and a choke-and-kill manifold that is capable of injecting a high pressure medium, such as drilling mud, through the flow line and spool into the well at a pressure that counterbalances any pressure tending to force the drill stem out of the well. The fluid medium injected into the well from the choke-and-kill manifold is also used to seal or shut in a well when such is desired.
Because the choke-and-kill flow line must be capable of handling the flow of fluid at very high pressure, i.e. in the order of 5,000 to 10,000 psi or greater, it is very difficult to provide a flexible flow conduit that will safely handle the choke-and-kill fluid. One should bear in mind also that it is imperative that the choke-and-kill manifold and the flow line interconnecting the manifold with the spool of the drilling wellhead apparatus be capable of functioning without failure because the choke-and-kill system is typically the last resort in preventing well blowouts from occurring. The flow line must not rupture or leak.
One problem occurs frequently, especially when drilling is being conducted from an offshore platform: The choke-and-kill flow line, if composed of rigid piping, is typically subjected to significant mechanical stresses which are induced by movement of the derrick and derrick support platform structure relative to one another. It is inevitable that some relative derrick, platform and drilling head movement will occur because of the frequency adverse conditions under which drilling is accomplished and because the platform construction, being composed largely of fabricated steel structure, reacts to various forces acting thereupon. Rigid flow lines interconnecting relatively movable objects could become excessively strained or fatigued and therefore rupture or leak under high pressure.
In the past, flexible conduits have been employed as choke-and-kill lines, but, as indicated above, when extremely high pressures are expected to be encountered, it is typically impractical to consider flexible flow line structures that will be capable of withstanding the internal pressure that could be applied thereto during choke-and-kill operations. Flow lines have been provided that incorporate rigid flow line sections, the various sections being interconnected by means of swivel joints that are variously oriented in such manner as to account for relative movement between the choke-and-kill manifold, which is mounted on the well drilling platform, and the spool structure of the well drilling apparatus, which is connected to a conductor conduit that extends downwardly through the platform apparatus and into the upper earth formation beneath the ocean floor. A major problem with swivel jointed flow line mechanisms that have been provided in the past is the fact that the swivel joints incorporate sealing elements that are incapable of withstanding the internal pressure applied thereto and yet remain movable under low torque. Further, the trust bearings of the swivel joint structures are easily contaminated with the fluid contained within the flow line, thereby causing rather rapid deterioration of the swivel joints themselves. Additionally, increase of pressure within presently available swivel joint constructions typically causes a subsequent increase in the friction retarding characteristics thereof which has a tendency to limit free movement of the swivel joint construction as well drilling operations are conducted. It is highly desirable therefore to provide a flow line construction for interconnection of the well drilling spool and the choke-and-kill manifold that will accommodate relative movement between the spool and the manifold and yet will maintain optimum sealing ability at all times.
Most swivel joint constructions incorporate bearing assemblies and seals that cannot be replaced by means of field repair. In the event seal leakage occurs or in the event bearings become worn to the point that replacement is necessary, the entire swivel joint conduit must be removed and transported to a suitable site for repair. Since drilling rig down time is critical, a replacement swivel joint conduit must be maintained on location, thereby adding to the expense of the drilling operation. In the alternative, the drilling operation can be discontinued until a replacement swivel joint conduit can be transported to the drilling site. It is desirable therefore to provide a swivel joint conduit mechanism wherein the bearings and seals thereof may be replaced by means of field repair.
It is therefore a primary feature of this invention to provide a novel swivel joint conduit assembly wherein the seals and bearings of each of the swivels thereof may be replaced by means of field repair.
It is also a feature of the present invention to provide a novel swivel joint construction for flow lines that incorporates pressure enhanced sealing elements that provide leak free swivel joint operation at all of the pressure ranges thereof.
It is another important feature of the present invention to provide a novel swivel joint construction for flow lines wherein the swivel joint structure incorporates thrust bearings and the seal structure of the swivel joint construction effectively prevents contamination of the bearings by the fluid controlled by the flow line.
Among the several features of the present invention is noted to be contemplation of a novel swivel joint construction for flow lines wherein a swivel joint housing structure is provided that is not a pressure containing structure, but rather only provides mechanical support to withstand the thrust loading that is applied thereto in response to the pressure contained within the swivel joint structure.
It is also a feature of the present invention to provide a novel swivel joint construction incorporating a pair of relatively movable hubs that are retained by a housing construction, the hubs being free for relative rotation throughout the entire pressure range of the swivel joint construction.
It is also an important feature of the present invention to provide a novel swivel joint construction for movable high pressure flow lines incorporating lubricating means that enable simple and efficient lubrication of the bearings of the swivel joint construction.
Other and further objects, advantages and features of the present invention will become apparent to one skilled in the art upon consideration of this entire disclosure. The form of the invention, which will now be described in detail, illustrates the general principles of the invention, but it is to be understood that this detailed description is not to be taken as limiting the scope of the present invention. For example, although the present invention is described principally as it relates to utilization in conjunction with offshore drilling rigs, especially of the platform type, it is not intended in any way to limit the present invention to any particular type of drilling rig nor is it intended to limit utilization of the present invention in conjunction with drilling rigs. It is intended that the invention may have application, within the spirit and scope of the present invention, in any environment where relatively movable objects are connected by a high pressure flow line.